crypto -- API for cryptographic services in the kernel
#include <opencrypto/cryptodev.h>
int32_t
crypto_get_driverid(u_int8_t);
int
crypto_register(u_int32_t, int, u_int16_t, u_int32_t,
int (*)(void *, u_int32_t *, struct cryptoini *),
int (*)(void *, u_int64_t), int (*)(void *, struct cryptop *),
void *);
int
crypto_kregister(u_int32_t, int, u_int32_t,
int (*)(void *, struct cryptkop *), void *);
int
crypto_unregister(u_int32_t, int);
int
crypto_unregister_all(u_int32_t);
void
crypto_done(struct cryptop *);
void
crypto_kdone(struct cryptkop *);
int
crypto_newsession(u_int64_t *, struct cryptoini *, int);
int
crypto_freesession(u_int64_t);
int
crypto_dispatch(struct cryptop *);
int
crypto_kdispatch(struct cryptkop *);
int
crypto_unblock(u_int32_t, int);
struct cryptop *
crypto_getreq(int);
void
crypto_freereq(void);
#define CRYPTO_SYMQ 0x1
#define CRYPTO_ASYMQ 0x2
#define EALG_MAX_BLOCK_LEN 16
struct cryptoini {
int cri_alg;
int cri_klen;
int cri_rnd;
caddr_t cri_key;
u_int8_t cri_iv[EALG_MAX_BLOCK_LEN];
struct cryptoini *cri_next;
};
struct cryptodesc {
int crd_skip;
int crd_len;
int crd_inject;
int crd_flags;
struct cryptoini CRD_INI;
struct cryptodesc *crd_next;
};
struct cryptop {
TAILQ_ENTRY(cryptop) crp_next;
u_int64_t crp_sid;
int crp_ilen;
int crp_olen;
int crp_etype;
int crp_flags;
caddr_t crp_buf;
caddr_t crp_opaque;
struct cryptodesc *crp_desc;
int (*crp_callback) (struct cryptop *);
caddr_t crp_mac;
};
struct crparam {
caddr_t crp_p;
u_int crp_nbits;
};
#define CRK_MAXPARAM 8
struct cryptkop {
TAILQ_ENTRY(cryptkop) krp_next;
u_int krp_op; /* ie. CRK_MOD_EXP or other */
u_int krp_status; /* return status */
u_short krp_iparams; /* # of input parameters */
u_short krp_oparams; /* # of output parameters */
u_int32_t krp_hid;
struct crparam krp_param[CRK_MAXPARAM];
int (*krp_callback)(struct cryptkop *);
};
crypto is a framework for drivers of cryptographic hardware to register
with the kernel so ``consumers'' (other kernel subsystems, and users
through the /dev/crypto device) are able to make use of it. Drivers register
with the framework the algorithms they support, and provide entry
points (functions) the framework may call to establish, use, and tear
down sessions. Sessions are used to cache cryptographic information in a
particular driver (or associated hardware), so initialization is not
needed with every request. Consumers of cryptographic services pass a
set of descriptors that instruct the framework (and the drivers registered
with it) of the operations that should be applied on the data (more
than one cryptographic operation can be requested).
Keying operations are supported as well. Unlike the symmetric operators
described above, these sessionless commands perform mathematical operations
using input and output parameters.
Since the consumers may not be associated with a process, drivers may not
sleep(9). The same holds for the framework. Thus, a callback mechanism
is used to notify a consumer that a request has been completed (the callback
is specified by the consumer on an per-request basis). The callback
is invoked by the framework whether the request was successfully completed
or not. An error indication is provided in the latter case. A
specific error code, EAGAIN, is used to indicate that a session number
has changed and that the request may be re-submitted immediately with the
new session number. Errors are only returned to the invoking function if
not enough information to call the callback is available (meaning, there
was a fatal error in verifying the arguments). For session initialization
and teardown there is no callback mechanism used.
The crypto_newsession() routine is called by consumers of cryptographic
services (such as the ipsec(4) stack) that wish to establish a new session
with the framework. On success, the first argument will contain the
Session Identifier (SID). The second argument contains all the necessary
information for the driver to establish the session. The third argument
indicates whether a hardware driver (1) should be used or not (0). The
various fields in the cryptoini structure are:
cri_alg Contains an algorithm identifier. Currently supported algorithms
are:
CRYPTO_DES_CBC
CRYPTO_3DES_CBC
CRYPTO_BLF_CBC
CRYPTO_CAST_CBC
CRYPTO_SKIPJACK_CBC
CRYPTO_MD5_HMAC
CRYPTO_SHA1_HMAC
CRYPTO_RIPEMD160_HMAC
CRYPTO_MD5_KPDK
CRYPTO_SHA1_KPDK
CRYPTO_AES_CBC
CRYPTO_ARC4
CRYPTO_MD5
CRYPTO_SHA1
CRYPTO_SHA2_HMAC
CRYPTO_NULL_HMAC
CRYPTO_NULL_CBC
cri_klen Specifies the length of the key in bits, for variable-size key
algorithms.
cri_rnd Specifies the number of rounds to be used with the algorithm,
for variable-round algorithms.
cri_key Contains the key to be used with the algorithm.
cri_iv Contains an explicit initialization vector (IV), if it does not
prefix the data. This field is ignored during initialization.
If no IV is explicitly passed (see below on details), a random
IV is used by the device driver processing the request.
cri_next Contains a pointer to another cryptoini structure. Multiple
such structures may be linked to establish multi-algorithm sessions
(ipsec(4) is an example consumer of such a feature).
The cryptoini structure and its contents will not be modified by the
framework (or the drivers used). Subsequent requests for processing that
use the SID returned will avoid the cost of re-initializing the hardware
(in essence, SID acts as an index in the session cache of the driver).
crypto_freesession() is called with the SID returned by
crypto_newsession() to disestablish the session.
crypto_dispatch() is called to process a request. The various fields in
the cryptop structure are:
crp_sid Contains the SID.
crp_ilen Indicates the total length in bytes of the buffer to be
processed.
crp_olen On return, contains the total length of the result. For
symmetric crypto operations, this will be the same as the
input length. This will be used if the framework needs to
allocate a new buffer for the result (or for re-formatting
the input).
crp_callback This routine is invoked upon completion of the request,
whether successful or not. It is invoked through the
crypto_done() routine. If the request was not successful,
an error code is set in the crp_etype field. It is the
responsibility of the callback routine to set the appropriate
spl(9) level.
crp_etype Contains the error type, if any errors were encountered, or
zero if the request was successfully processed. If the
EAGAIN error code is returned, the SID has changed (and has
been recorded in the crp_sid field). The consumer should
record the new SID and use it in all subsequent requests.
In this case, the request may be re-submitted immediately.
This mechanism is used by the framework to perform session
migration (move a session from one driver to another,
because of availability, performance, or other considerations).
Note that this field only makes sense when examined by the
callback routine specified in crp_callback. Errors are
returned to the invoker of crypto_process() only when
enough information is not present to call the callback routine
(i.e., if the pointer passed is NULL or if no callback
routine was specified).
crp_flags Is a bitmask of flags associated with this request. Currently
defined flags are:
CRYPTO_F_IMBUF The buffer pointed to by crp_buf is an mbuf
chain.
crp_buf Points to the input buffer. On return (when the callback
is invoked), it contains the result of the request. The
input buffer may be an mbuf chain or a contiguous buffer,
depending on crp_flags.
crp_opaque This is passed through the crypto framework untouched and
is intended for the invoking application's use.
crp_desc This is a linked list of descriptors. Each descriptor provides
information about what type of cryptographic operation
should be done on the input buffer. The various
fields are:
crd_skip The offset in the input buffer where processing
should start.
crd_len How many bytes, after crd_skip, should be processed.
crd_inject Offset from the beginning of the buffer to
insert any results. For encryption algorithms,
this is where the initialization vector (IV)
will be inserted when encrypting or where it
can be found when decrypting (subject to
crd_flags). For MAC algorithms, this is where
the result of the keyed hash will be inserted.
crd_flags The following flags are defined:
CRD_F_ENCRYPT For encryption algorithms,
this bit is set when encryption
is required (when not
set, decryption is performed).
CRD_F_IV_PRESENT For encryption algorithms,
this bit is set when the IV
already precedes the data,
so the crd_inject value will
be ignored and no IV will be
written in the buffer. Otherwise,
the IV used to
encrypt the packet will be
written at the location
pointed to by crd_inject.
The IV length is assumed to
be equal to the blocksize of
the encryption algorithm.
Some applications that do
special ``IV cooking'', such
as the half-IV mode in
ipsec(4), can use this flag
to indicate that the IV
should not be written on the
packet. This flag is typically
used in conjunction
with the CRD_F_IV_EXPLICIT
flag.
CRD_F_IV_EXPLICIT For encryption algorithms,
this bit is set when the IV
is explicitly provided by
the consumer in the cri_iv
fields. Otherwise, for
encryption operations the IV
is provided for by the
driver used to perform the
operation, whereas for
decryption operations it is
pointed to by the crd_inject
field. This flag is typically
used when the IV is
calculated ``on the fly'' by
the consumer, and does not
precede the data (some
ipsec(4) configurations, and
the encrypted swap are two
such examples).
CRD_F_COMP For compression algorithms,
this bit is set when compression
is required (when
not set, decompression is
performed).
CRD_INI This cryptoini structure will not be modified
by the framework or the device drivers. Since
this information accompanies every cryptographic
operation request, drivers may re-initialize
state on-demand (typically an expensive
operation). Furthermore, the cryptographic
framework may re-route requests as a result of
full queues or hardware failure, as described
above.
crd_next Point to the next descriptor. Linked operations
are useful in protocols such as ipsec(4),
where multiple cryptographic transforms may be
applied on the same block of data.
crypto_getreq() allocates a cryptop structure with a linked list of as
many cryptodesc structures as were specified in the argument passed to
it.
crypto_freereq() deallocates a structure cryptop and any cryptodesc
structures linked to it. Note that it is the responsibility of the callback
routine to do the necessary cleanups associated with the opaque
field in the cryptop structure.
crypto_kdispatch() is called to perform a keying operation. The various
fields in the cryptkop structure are:
krp_op Operation code, such as CRK_MOD_EXP.
krp_status Return code. This errno-style variable indicates whether
lower level reasons for operation failure.
krp_iparams Number if input parameters to the specified operation.
Note that each operation has a (typically hardwired) number
of such parameters.
krp_oparams Number if output parameters from the specified operation.
Note that each operation has a (typically hardwired) number
of such parameters.
krp_kvp An array of kernel memory blocks containing the parameters.
krp_hid Identifier specifying which low-level driver is being
used.
krp_callback Callback called on completion of a keying operation.
The crypto_get_driverid(), crypto_register(), crypto_kregister(),
crypto_unregister(), crypto_unblock(), and crypto_done() routines are
used by drivers that provide support for cryptographic primitives to register
and unregister with the kernel crypto services framework. Drivers
must first use the crypto_get_driverid() function to acquire a driver
identifier, specifying the cc_flags as an argument (normally 0, but software-only
drivers should specify CRYPTOCAP_F_SOFTWARE). For each algorithm
the driver supports, it must then call crypto_register(). The
first two arguments are the driver and algorithm identifiers. The next
two arguments specify the largest possible operator length (in bits,
important for public key operations) and flags for this algorithm. The
last four arguments must be provided in the first call to
crypto_register() and are ignored in all subsequent calls. They are
pointers to three driver-provided functions that the framework may call
to establish new cryptographic context with the driver, free already
established context, and ask for a request to be processed (encrypt,
decrypt, etc.); and an opaque parameter to pass when calling each of
these routines. crypto_unregister() is called by drivers that wish to
withdraw support for an algorithm. The two arguments are the driver and
algorithm identifiers, respectively. Typically, drivers for PCMCIA
crypto cards that are being ejected will invoke this routine for all
algorithms supported by the card. crypto_unregister_all() will unregister
all algorithms registered by a driver and the driver will be disabled
(no new sessions will be allocated on that driver, and any existing sessions
will be migrated to other drivers). The same will be done if all
algorithms associated with a driver are unregistered one by one.
The calling convention for the three driver-supplied routines is:
int (*newsession)(void *, u_int32_t *, struct cryptoini *);
int (*freesession)(void *, u_int64_t);
int (*process)(void *, struct cryptop *);
int (*kprocess)(void *, struct cryptkop *);
On invocation, the first argument to all routines is an opaque data value
supplied when the algorithm is registered with crypto_register(). The
second argument to newsession() contains the driver identifier obtained
via crypto_get_driverid(). On successful return, it should contain a
driver-specific session identifier. The third argument is identical to
that of crypto_newsession().
The freesession() routine takes as arguments the opaque data value and
the SID (which is the concatenation of the driver identifier and the
driver-specific session identifier). It should clear any context associated
with the session (clear hardware registers, memory, etc.).
The process() routine is invoked with a request to perform crypto processing.
This routine must not block, but should queue the request and
return immediately. Upon processing the request, the callback routine
should be invoked. In case of an unrecoverable error, the error indication
must be placed in the crp_etype field of the cryptop structure.
When the request is completed, or an error is detected, the process()
routine should invoke crypto_done(). Session migration may be performed,
as mentioned previously.
In case of a temporary resource exhaustion, the process() routine may
return ERESTART in which case the crypto services will requeue the
request, mark the driver as ``blocked'', and stop submitting requests for
processing. The driver is then responsible for notifying the crypto services
when it is again able to process requests through the
crypto_unblock() routine. This simple flow control mechanism should only
be used for short-lived resource exhaustion as it causes operations to be
queued in the crypto layer. Doing so is preferable to returning an error
in such cases as it can cause network protocols to degrade performance by
treating the failure much like a lost packet.
The kprocess() routine is invoked with a request to perform crypto key
processing. This routine must not block, but should queue the request
and return immediately. Upon processing the request, the callback routine
should be invoked. In case of an unrecoverable error, the error
indication must be placed in the krp_status field of the cryptkop structure.
When the request is completed, or an error is detected, the
kprocess() routine should invoked crypto_kdone().
crypto_register(), crypto_kregister(), crypto_unregister(),
crypto_newsession(), crypto_freesession(), and crypto_unblock() return 0
on success, or an error code on failure. crypto_get_driverid() returns a
non-negative value on error, and -1 on failure. crypto_getreq() returns
a pointer to a cryptop structure and NULL on failure. crypto_dispatch()
returns EINVAL if its argument or the callback function was NULL, and 0
otherwise. The callback is provided with an error code in case of failure,
in the crp_etype field.
sys/opencrypto/crypto.c most of the framework code
ipsec(4), malloc(9), sleep(9)
The cryptographic framework first appeared in OpenBSD 2.7 and was written
by Angelos D. Keromytis <[email protected]>.
The framework currently assumes that all the algorithms in a
crypto_newsession() operation must be available by the same driver. If
that is not the case, session initialization will fail.
The framework also needs a mechanism for determining which driver is best
for a specific set of algorithms associated with a session. Some type of
benchmarking is in order here.
Multiple instances of the same algorithm in the same session are not supported.
Note that 3DES is considered one algorithm (and not three
instances of DES). Thus, 3DES and DES could be mixed in the same
request.
FreeBSD 5.2.1 October 14, 2002 FreeBSD 5.2.1 [ Back ] |
